<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
    <style>
      .floatBox {
        /* float: left; */
        height: 200px;
      }
      .first {
        float: left;
        width: 200px;
        background: pink;
      }
      .second {
        overflow: auto;
        /* width: calc(100% - 200px); */
        background-color: aqua;
      }
    </style>
  </head>
  <body>
    <div class="container">
      <div class="floatBox first"></div>
      <div class="floatBox second"></div>
    </div>
  </body>
</html>
